Resonance effects in the nonadiabatic nonlinear quantum dimer

In the presence of 1/f ^β noise, we investigate the logical stochastic resonance (LSR) in an asymmetric bistable model driven by various cycling combinations of two logic inputs. The probability of correct logic outputs is calculated according to true table of logic relationships. Two major results are presented. Firstly, it is shown that the LSR effect can be obtained by changing noise strength. Over entire range of noise variance, white noise can be considered to be better than 1/f noise or 1/f ² noise to obtain clean logic operation. At a smaller noise level, 1/f noise can realize higher output probability than white noise or 1/f ² noise. In the sense, 1/f noise can be considered to be better than white noise or 1/f ². On the other hand, the correct probability can evolves nonmonotonically as noise exponent β increases, and a kind of SR-like effect can be obtained as a result of β. At certain intermediate noise variance, the output probability is able to attain its minimum at β = 1. It is also shown that actually some finite β sometime can be better than β = 0 at small range of noise variance. The study might provide some potential complement to LSR effect in the presence of 1/f ^β noise.     

Biased Diffusion with Correlated Noise

The diffusion of hard-core particles subject to a global bias is described by a nonlinear, anisotropic generalization of the diffusion equation with conserved, local noise. Using renormalization group techniques, we analyze the effect of an additional noise term, with spatially long-ranged correlations, on the long-time, long-wavelength behavior of this model. Above an upper critical dimension d _LR, the long-ranged noise is always relevant. In contrast, for d<d _LR, we find a weak noise regime dominated by short-range noise. As the range of the noise correlations increases, an intricate sequence of stability exchanges between different fixed points of the renormalization group occurs. Both smooth and discontinuous crossovers between the associated universality classes are observed, reflected in the scaling exponents. We discuss the necessary techniques in some detail since they are applicable to a much wider range of problems.     

Effects on generalized growth models driven by a non-Poissonian dichotomic noise

In this paper we consider a general growth model with stochastic growth rate modelled via a symmetric non-poissonian dichotomic noise. We find an exact analytical solution for its probability distribution. We consider the, as yet, unexplored case where the deterministic growth rate is perturbed by a dichotomic noise characterized by a waiting time distribution in the two state that is a power law with power 1 < μ < 2. We apply the results to two well-known growth models; Malthus-Verhulst and Gompertz.     

Harmonic stochastic resonance-enhanced signal detecting in NW small-world neural network

The harmonic stochastic resonance-enhanced signal detecting in Newman-Watts small-world neural network is studied using the Hodgkin-Huxley dynamical equation with noise.If the connection probability p,coupling strength g syn and noise intensity D matches well,higher order resonance will be found and an optimal signal-to-noise ratio will be obtained.Then,the reasons are given to explain the mechanism of this appearance.     

A practical prediction method for the stochastic insulation effect of a sound barrier with arbitrary random noise excitation

A sound barrier is often used as a typical noise control device to modify sound propagation characteristics. Also, statistical parameters such as the median value of sound level, $\text{L}{}_{\mathrm{x}}$, as well as the lower order statistical values of sound energy or level, are important for noise evaluation and regulation problems. In this paper, a new trial of statistical prediction for the stochastic insulation effect of a sound barrier is proposed in a special case where the insulation system parameters have to be improved, especially from a methodological viewpoint. Moreover, the improved probability density function (pdf) of output response corresponding to the above parameter change is expressed in the general form of a statistical series expansion taking the original pdf before the system improvement as the first expansion term. The experimental results of applying it in trial to the actual noise data are in good agreement with theory.     

基于双谱估计的BL Lac天体S5 0716+714光变周期

大幅度、快速光变是BL Lac天体的重要特征之一,光变研究对探索BL Lac天体内部的物理过程和机理具有特殊的意义.从大量文献中收集了BL Lac天体S5 0716+714光学V,R,I 3个波段从1994年到2008年的有效观测数据,并将这些数据30天平均后进行自回归模型(AR)的双谱估计. 双谱的等高线图和对角切片图表明,双谱估计能消除噪声的干扰来提取有用信息,抑制了噪声、提高了信噪比,有很高的分辨率,避免了伪峰的出现,能准确地认证BL Lac天体的光变周期值.由V,R,I 3个波段的双谱等高线图和对     

Kerr效应和虚光场效应对三能级原子-场系统原子占居态几率的影响

研究类克尔介质中非旋波近似下三能级原子与场相互作用系统的原子占居态几率的时间演化;讨论了光场频率ω及类克尔介质常量x对原子占居态几率的影响。结果表明:虚光场的作用使原子占居态几率的时间演化曲线中出现量子噪音,而Kerr介质效应会抑制量子噪音的产生;原子吸收率随x的增大而降低;系统的粒子数反转随x的增大明显减弱,但随ω的增大有所增强。     

A study on the action of non-Gaussian noise on a Brownian particle

We analytically address the non-equilibrium problem of a Brownian particle in contact with a thermal reservoir by means of a non-Gaussian Langevin noise term η(t)$\eta \left(t\right)$. The presence of noise kurtosis is akin to a second temperature reservoir acting on the system, and we exploit its consequences by means of studying a converging exact form for the stationary probability distribution.     

The influence of noise on the logistic model

The behavior of the logistic system which is generated by the functionf(x =ax (1–x) changes in an interesting way if it is perturbed by external noise. It turns out that the chaotic behavior which was predicted by Li and Yorke for orbits of period 3, becomes visible and that a sequence of mergence transitions occurs at the critical parameter. The change of the invariant probability density and the Lyapunov exponents are examined numerically. The power spectrum for the period 3 orbit for different fluctuations is calculated and a recursion formula for the time evolution of the probability density is presented as a discrete-time analog of a Chapman-Kolmogorov equation.     

Detecting and quantifying temporal correlations in stochastic resonance via information theory measures

We show that Information Theory quantifiers are suitable tools for detecting and for quantifying noise-induced temporal correlations in stochastic resonance phenomena. We use the Bandt & Pompe (BP) method [Phys. Rev. Lett. 88, 174102 (2002)] to define a probability distribution, P, that fully characterizes temporal correlations. The BP method is based on a comparison of neighboring values, and here is applied to the temporal sequence of residence-time intervals generated by the paradigmatic model of a Brownian particle in a sinusoidally modulated bistable potential. The probability distribution P generated via the BP method has associated a normalized Shannon entropy, H[P], and a statistical complexity measure, C[P], which is defined as proposed by Rosso et al. [Phys. Rev. Lett. 99, 154102 (2007)]. The statistical complexity quantifies not only randomness but also the presence of correlational structures, the two extreme circumstances of maximum knowledge (“perfect order") and maximum ignorance (“complete randomness") being regarded an “trivial", and in consequence, having complexity C = 0. We show that both, H and C, display resonant features as a function of the noise intensity, i.e., for an optimal level of noise the entropy displays a minimum and the complexity, a maximum. This resonant behavior indicates noise-enhanced temporal correlations in the sequence of residence-time intervals. The methodology proposed here has great potential for the precise detection of subtle signatures of noise-induced temporal correlations in real-world complex signals.     

Bifurcations in fluctuating systems: The center-manifold approach

Bifurcations in fluctuating dynamical systems are studied using the ideas of center-manifold reduction. The method provides not only a systematic procedure for the reduction of the system to a small number of variables-but also a classification scheme for the different kinds of dynamical behavior possible near bifurcation points. The joint probability density factorizes into a stationary Gaussian densityp(v/u) in the fast variablesv, and a time-dependent densityP(u, f) in the slow variablesu describing the dynamics on the center manifoldv=v₀ (u). P(u, t) obeys a reduced Fokker-Planck equation that can be written in a normal form by means of local nonlinear transformations. Both additive and multiplicative white noise are considered, as is colored noise. The results extend and formalize Haken's concept of adiabatic elimination of fast variables.     

Dynamics of the infinite-ranged Potts model

We formulate a theory of single-spin-flip dynamics for the infinite-rangeq-state Potts model. We derive a Fokker-Planck equation, without diffusive term, from a phenomenological master equation. It describes the approach to equilibrium of the time-dependent probability density and thus generalizes Griffiths' (1966) result for the Ising model. We particularly compare the dynamic evolutions ofq=2 andq=3 systems when sinusoidal external fields are applied. In the caseq=2 we find evidence of a nonequilibrium phase transition and forq=3 period doubling bifurcations are observed, yielding a good estimate of Feigenbaum's universal exponent.     

On‐site analysis of Chinese Cloisonné enamels from fifteenth to nineteenth centuries

A selection of 22 rare Chinese cloisonné enamels, from fifteenth century to nineteenth century A.D ., has been studied on‐site in the storage rooms of the musée des Arts décoratifs in Paris. The Raman signatures of the transparent and/or opacified glass matrix are discussed and compared with those that were previously recorded on glazed pottery, enameled and stained glasses. Enamels mostly belong to lead‐based potash‐lime glasses. Three different compositions, lead‐potash‐lime (fifteenth, sixteenth, eighteenth and nineteenth century), soda‐rich (sixteenth–seventeenth century) and soda‐lime (seventeenth century) are identified according to the wavenumber maxima of the Si O stretching and bending multiplets. Most of the pigment signatures are similar to those recorded on ceramic glazes and glass enamels, which proves the link between the technologies but a specific opacifier is observed: fluorite (CaF₂). Naples Yellow pigment variations give characteristic signatures. Additionally, a comparison is made with Limoges enamels (sixteenth–nineteenth century A.D. ). Copyright © 2009 John Wiley & Sons, Ltd.     

Identification of the origin of monojet signatures at the LHC

Several new physics scenarios can lead to monojet signatures at the LHC. If such events are observed above the Standard Model background it will be important to identify their origin. In this Letter we compare and contrast these signatures as produced in two very different pictures: vector or scalar unparticle production in the scale-invariant/conformal regime and graviton emission in the Arkani-Hamed, Dimopoulos and Dvali extra-dimensional model. We demonstrate that these two scenarios can be distinguished at the LHC for a reasonable range of model parameters through the shape of their respective monojet and/or missing E_T distributions.     

Escape driven by strongly correlated noise

We consider the colored-noise-driven archetypal bistability dynamics of the Ginzburg-Landau type. The focus is on the stationary behavior and the problem of escape from metastable states. The deterministic flow of the underlyingtwo-variable Fokker-Planck process is studied as a function of the noise correlation time . As a main result we find that the separatrix exhibits a cusp at asymptotically large noise color. The stationary probability is evaluated approximately (unified colored noise approximation) and compared with numerical exact results. The stationary probability forms the key input in the evaluation of the rate of escape. At very strong noise color, the escape path closely follows a nodal line, passing through the corresponding stable node. The asymptotic result for the escape rate at large is compared with exact calculations for the lowest, nonvanishing eigenvalue.     

Stationary Properties and Stochastic Resonance for a Saturation Laser Model with Cross-correlation Between Quantum Noise Terms

The stationary properties of a saturation laser model with cross-correlation between the real and imaginary parts of the quantum noise are investigated theoretically. Using the Novikov theorem and the Sargent technique, we obtain the analytic expressions of the stationary probability density distribution, the mean, the variance and the skewness of the saturation laser model. The cross-correlation coefficient λ and other parameters can make the stationary probability density distribution P _st (I) generate interesting two-extrema structure, one-extremum structure, or no-extremum structure. It is clearly found that a first- order-like-transition is induced by the coupling strength |λ| of the complex quantum noise terms in the saturation laser model. When the laser system is operated above the threshold, the mean 〈I〉 becomes larger and the output of the laser intensity increases; however the coupling strength |λ| attenuates the output of the laser intensity. When the laser is operated near and below the threshold, the mean 〈I〉 becomes smaller, the output of the laser intensity decreases, and |λ| still attenuates the output of the laser intensity. When a periodic signal is added to a saturation laser model with cross-correlation between quantum noise terms, the interesting stochastic resonance phenomena occur at λ=0. The noise intensity Q decreases the values of the resonance peak, however, the amplitude of the periodic signal B enhances the values of the resonance peak.     

Transport as a consequence of state-dependent diffusion

Overdamped particles subject to a drift in a force field with sinusoidal space dependence and also a sinusoidally modulated space-dependent diffusion, with the same period as the drift, experience a net driving force. The resulting current depends on the amplitude of the modulation of the diffusion and is a periodic function of the phase difference between the sinusoidal drift and the sinusoidal modulation of the diffusion. For small modulation amplitudes a particle subject to state-dependent noise behaves the same way as a particle subject to thermal noise but with a drift which, in addition to the sinusoidal term, contains a net force term [M. Büttiker,Z. Phys. B 68:161 (1987)]. A specific example of this behavior [N. G. van Kampen,IBM J. Res. Dev. 32:107 (1988); R. Landauer,J. Stat. Phys. 53:233 (1988).] is the motion of overdamped particles in a ring subject to a nonuniform temperature field. When the drift and the temperature, which are periodic with a period equal to the ring circumference, are not in phase a noise-induced circulating current results.This paper will appear in a forthcoming issue of theJournal of Statistical Physics.     

“Escape” of a periodically driven particle from a metastable state in a noisy system

We consider the statistical properties of the escape time of a particle initially sitting in a potential well subject to a combination of white noise and a periodic forcing term. As one finds in the case of the much-studied bistable potential, different kinds of resonant effects can occur, as measured by the survival probability and the average residence time. When this time is considered as a function of the noise strength, then we show that for small amplitudes of the forcing term there are no resonant effects, while for large amplitudes such effects can appear. We also show that a resonant phenomenon is possible in terms of the amplitude of a periodic forcing term.     

Stratonovich model driven by dichotomous noise: analytical results

Stationary and dynamic properties of the Stratonovich model driven by a dichotomous Markovian process (DMP) are investigated analytically. The stationary probability densityp _st and its moments are calculated exactly and the shape ofp _st is discussed in the whole parameter region. The location of the maxima ofp _st shows a behaviour similar to order parameters in continuous phase transitions. The time dependence of moments and the probability density is studied investigating (i) a series expansion of the formal solution for a given realization of the driving process, and (ii) the analytic behaviour of the Laplace transform of the probability density. As a function of physical parameters, qualitative changes of the long time behaviour may occur. Method (i) is generalized to determine the dynamics of moments for a superposition of independent DMP's (pregaussian noise).     

Can colored noise improve stochastic resonance?

The phenomenon of stochastic resonance is studied in the presence of colored noise. Several sources of colored noise are introduced and the consequences for the asymptotic time-periodic probability and the (phase-averaged) power spectrum are discussed. Based on space-time symmetry considerations, selection rules for the occurrence of-spikes in the power spectrum are derived. The effect of colored noise on the amplification of small periodic signals is studied in terms of effective, time-periodic Fokker-Planck equations: In overdamped systems driven by colored noise, we find that SR is suppressed with increasing noise color. In contrast, for colored noise induced by inertia (as well as for asymmetric dichotomic noise), one obtains an enhancement of SR. This latter result is obtained by studying the Kramers equation perturbed by a small periodic force.